The invention relates to a method of manufacturing a cathode ray tube, which tube comprises an envelope having a longitudinal axis and a gun assembly having a longitudinal axis and assembled on a mount in which:
a. the envelope is fixed in an assembly device in a given position;
b. the place and/or angle orientations of the gun assembly are adjusted;
c. the gun assembly is fixed in the adjusted orientation against non-axial movement;
d. the gun assembly is inserted into the neck of the envelope so that the said axes substantially coincide; and
e. the mount is sealed to the neck of the envelope.
A cathode ray tube may be, for example, a television camera tube or a display tube. Display tubes have a wide field of application. They may be used, for example, as a color or projection television tube, an oscilloscope tube, a color display tube and a DGD (data graphic display) tube. All these types of tubes comprise a gun assembly to generate at least one electron beam. Said electron beam must arrive in the deflection fields in a very particular manner and land in the tube in a very particular place on a target, for example, a display screen. Therefore, a very accurate placement of the gun assembly in the envelope during the manufacture of the tube is necessary.
A method as described hereinbefore is known from DE-A 2706420. The adjusted place and/or angle orientations of the gun assembly are fixed in said method by clamping an exhaust tubulation extending from the gun mount. When the gun assembly is inserted into the tube neck, stresses may be built up in the gun assembly. Moreover, stresses may arise in the gun assembly and glass mount during mounting, notably at the area of the connection of the gun assembly to the mount. During sealing of the mount to the neck of the envelope, the mount is softened during heating. As a result, the connection of the gun assembly to the mount becomes less stable because the said stresses can be relieved, so that variations in shape and movements of the gun assembly can occur. The adjusted orientation of the gun assembly consequently loses the desired accuracy.
It is, therefore, the object of the invention to provide a method of manufacturing a cathode ray tube in which the adjusted orientation of the gun assembly is maintained during sealing.